Kevin Hall via Xenomai <[email protected]> writes:
> Hi, > > > Is OOB I/O service a candidate for an EtherNet-based fieldbus protocol? I > read in a comment that it only applies to VLAN-tagged IP protocols, but I > don't know how old that is or if things have changed. I am able to send and > receive packets when using send() and recv(), but since these are not > out-of-band, I am often times seeing large delays in the processing of > data. That's why I am trying to use oob_read(...) and oob_write(...). > > > Additional Information: I am using Xenomai 5.15 with a Raspberry Pi 4. The > fieldbus protocol is EtherCAT (0x88a4). > > oob_read/write is independent from the EVL net mini-stack, this is a generic API for talking to oob-capable drivers. The mini-stack implements such a driver, which at the moment can (only) send/receive raw ethernet packets via common ethernet drivers. To get this done, we need a way to distinguish between regular and oob traffic, this is where VLAN tagging comes into play. Some VLANs can be assigned to oob traffic, handled by the mini-stack as such instead of leaving it to the regular network stack for processing (see evl_net_ether_accept() in kernel/evl/net/input.c which deals with ingress traffic). -- Philippe.
